Evaluation of the water penetration depth in mortar using water indicator and hyperspectral imaging

Water penetration is a potential cause of premature deterioration of reinforced concrete structures. The water indicator used for water detection cannot detect water penetration depths in samples containing high amount of blast furnace slag (BFS). Hence, hyperspectral imaging (HSI) was introduced in this study. Mortar specimens with different water-to-binder (w/b) ratios and BFS replacements were prepared. The moisture content distribution, water indicator, and HSI were used to measure the water penetration depth in the samples after water absorption exposure. The effects of the pore size and moisture content on the mechanisms of the water indicator were also investigated. HSI successfully detected the penetration depth of water in all mortar samples, even in those where detection by using the water indicator was not possible. The moisture content distribution and HSI yielded similar results for water penetration depths. The water penetration depths measured by applying the water indicator and HSI were similar in the mortars without BFS substitution. The water indicator underestimated the water penetration depths in the samples that contained BFS. The amount free water in the pores of mortar was the main factor controlling the applicability of the water indicator.